Use dentry_path() to create full path to inode object
[pohmelfs.git] / drivers / block / brd.c
blobec246437f5a44273911f6f6358f2a1fcc409478d
1 /*
2 * Ram backed block device driver.
4 * Copyright (C) 2007 Nick Piggin
5 * Copyright (C) 2007 Novell Inc.
7 * Parts derived from drivers/block/rd.c, and drivers/block/loop.c, copyright
8 * of their respective owners.
9 */
11 #include <linux/init.h>
12 #include <linux/module.h>
13 #include <linux/moduleparam.h>
14 #include <linux/major.h>
15 #include <linux/blkdev.h>
16 #include <linux/bio.h>
17 #include <linux/highmem.h>
18 #include <linux/mutex.h>
19 #include <linux/radix-tree.h>
20 #include <linux/fs.h>
21 #include <linux/slab.h>
23 #include <asm/uaccess.h>
25 #define SECTOR_SHIFT 9
26 #define PAGE_SECTORS_SHIFT (PAGE_SHIFT - SECTOR_SHIFT)
27 #define PAGE_SECTORS (1 << PAGE_SECTORS_SHIFT)
30 * Each block ramdisk device has a radix_tree brd_pages of pages that stores
31 * the pages containing the block device's contents. A brd page's ->index is
32 * its offset in PAGE_SIZE units. This is similar to, but in no way connected
33 * with, the kernel's pagecache or buffer cache (which sit above our block
34 * device).
36 struct brd_device {
37 int brd_number;
39 struct request_queue *brd_queue;
40 struct gendisk *brd_disk;
41 struct list_head brd_list;
44 * Backing store of pages and lock to protect it. This is the contents
45 * of the block device.
47 spinlock_t brd_lock;
48 struct radix_tree_root brd_pages;
52 * Look up and return a brd's page for a given sector.
54 static DEFINE_MUTEX(brd_mutex);
55 static struct page *brd_lookup_page(struct brd_device *brd, sector_t sector)
57 pgoff_t idx;
58 struct page *page;
61 * The page lifetime is protected by the fact that we have opened the
62 * device node -- brd pages will never be deleted under us, so we
63 * don't need any further locking or refcounting.
65 * This is strictly true for the radix-tree nodes as well (ie. we
66 * don't actually need the rcu_read_lock()), however that is not a
67 * documented feature of the radix-tree API so it is better to be
68 * safe here (we don't have total exclusion from radix tree updates
69 * here, only deletes).
71 rcu_read_lock();
72 idx = sector >> PAGE_SECTORS_SHIFT; /* sector to page index */
73 page = radix_tree_lookup(&brd->brd_pages, idx);
74 rcu_read_unlock();
76 BUG_ON(page && page->index != idx);
78 return page;
82 * Look up and return a brd's page for a given sector.
83 * If one does not exist, allocate an empty page, and insert that. Then
84 * return it.
86 static struct page *brd_insert_page(struct brd_device *brd, sector_t sector)
88 pgoff_t idx;
89 struct page *page;
90 gfp_t gfp_flags;
92 page = brd_lookup_page(brd, sector);
93 if (page)
94 return page;
97 * Must use NOIO because we don't want to recurse back into the
98 * block or filesystem layers from page reclaim.
100 * Cannot support XIP and highmem, because our ->direct_access
101 * routine for XIP must return memory that is always addressable.
102 * If XIP was reworked to use pfns and kmap throughout, this
103 * restriction might be able to be lifted.
105 gfp_flags = GFP_NOIO | __GFP_ZERO;
106 #ifndef CONFIG_BLK_DEV_XIP
107 gfp_flags |= __GFP_HIGHMEM;
108 #endif
109 page = alloc_page(gfp_flags);
110 if (!page)
111 return NULL;
113 if (radix_tree_preload(GFP_NOIO)) {
114 __free_page(page);
115 return NULL;
118 spin_lock(&brd->brd_lock);
119 idx = sector >> PAGE_SECTORS_SHIFT;
120 if (radix_tree_insert(&brd->brd_pages, idx, page)) {
121 __free_page(page);
122 page = radix_tree_lookup(&brd->brd_pages, idx);
123 BUG_ON(!page);
124 BUG_ON(page->index != idx);
125 } else
126 page->index = idx;
127 spin_unlock(&brd->brd_lock);
129 radix_tree_preload_end();
131 return page;
134 static void brd_free_page(struct brd_device *brd, sector_t sector)
136 struct page *page;
137 pgoff_t idx;
139 spin_lock(&brd->brd_lock);
140 idx = sector >> PAGE_SECTORS_SHIFT;
141 page = radix_tree_delete(&brd->brd_pages, idx);
142 spin_unlock(&brd->brd_lock);
143 if (page)
144 __free_page(page);
147 static void brd_zero_page(struct brd_device *brd, sector_t sector)
149 struct page *page;
151 page = brd_lookup_page(brd, sector);
152 if (page)
153 clear_highpage(page);
157 * Free all backing store pages and radix tree. This must only be called when
158 * there are no other users of the device.
160 #define FREE_BATCH 16
161 static void brd_free_pages(struct brd_device *brd)
163 unsigned long pos = 0;
164 struct page *pages[FREE_BATCH];
165 int nr_pages;
167 do {
168 int i;
170 nr_pages = radix_tree_gang_lookup(&brd->brd_pages,
171 (void **)pages, pos, FREE_BATCH);
173 for (i = 0; i < nr_pages; i++) {
174 void *ret;
176 BUG_ON(pages[i]->index < pos);
177 pos = pages[i]->index;
178 ret = radix_tree_delete(&brd->brd_pages, pos);
179 BUG_ON(!ret || ret != pages[i]);
180 __free_page(pages[i]);
183 pos++;
186 * This assumes radix_tree_gang_lookup always returns as
187 * many pages as possible. If the radix-tree code changes,
188 * so will this have to.
190 } while (nr_pages == FREE_BATCH);
194 * copy_to_brd_setup must be called before copy_to_brd. It may sleep.
196 static int copy_to_brd_setup(struct brd_device *brd, sector_t sector, size_t n)
198 unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT;
199 size_t copy;
201 copy = min_t(size_t, n, PAGE_SIZE - offset);
202 if (!brd_insert_page(brd, sector))
203 return -ENOMEM;
204 if (copy < n) {
205 sector += copy >> SECTOR_SHIFT;
206 if (!brd_insert_page(brd, sector))
207 return -ENOMEM;
209 return 0;
212 static void discard_from_brd(struct brd_device *brd,
213 sector_t sector, size_t n)
215 while (n >= PAGE_SIZE) {
217 * Don't want to actually discard pages here because
218 * re-allocating the pages can result in writeback
219 * deadlocks under heavy load.
221 if (0)
222 brd_free_page(brd, sector);
223 else
224 brd_zero_page(brd, sector);
225 sector += PAGE_SIZE >> SECTOR_SHIFT;
226 n -= PAGE_SIZE;
231 * Copy n bytes from src to the brd starting at sector. Does not sleep.
233 static void copy_to_brd(struct brd_device *brd, const void *src,
234 sector_t sector, size_t n)
236 struct page *page;
237 void *dst;
238 unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT;
239 size_t copy;
241 copy = min_t(size_t, n, PAGE_SIZE - offset);
242 page = brd_lookup_page(brd, sector);
243 BUG_ON(!page);
245 dst = kmap_atomic(page, KM_USER1);
246 memcpy(dst + offset, src, copy);
247 kunmap_atomic(dst, KM_USER1);
249 if (copy < n) {
250 src += copy;
251 sector += copy >> SECTOR_SHIFT;
252 copy = n - copy;
253 page = brd_lookup_page(brd, sector);
254 BUG_ON(!page);
256 dst = kmap_atomic(page, KM_USER1);
257 memcpy(dst, src, copy);
258 kunmap_atomic(dst, KM_USER1);
263 * Copy n bytes to dst from the brd starting at sector. Does not sleep.
265 static void copy_from_brd(void *dst, struct brd_device *brd,
266 sector_t sector, size_t n)
268 struct page *page;
269 void *src;
270 unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT;
271 size_t copy;
273 copy = min_t(size_t, n, PAGE_SIZE - offset);
274 page = brd_lookup_page(brd, sector);
275 if (page) {
276 src = kmap_atomic(page, KM_USER1);
277 memcpy(dst, src + offset, copy);
278 kunmap_atomic(src, KM_USER1);
279 } else
280 memset(dst, 0, copy);
282 if (copy < n) {
283 dst += copy;
284 sector += copy >> SECTOR_SHIFT;
285 copy = n - copy;
286 page = brd_lookup_page(brd, sector);
287 if (page) {
288 src = kmap_atomic(page, KM_USER1);
289 memcpy(dst, src, copy);
290 kunmap_atomic(src, KM_USER1);
291 } else
292 memset(dst, 0, copy);
297 * Process a single bvec of a bio.
299 static int brd_do_bvec(struct brd_device *brd, struct page *page,
300 unsigned int len, unsigned int off, int rw,
301 sector_t sector)
303 void *mem;
304 int err = 0;
306 if (rw != READ) {
307 err = copy_to_brd_setup(brd, sector, len);
308 if (err)
309 goto out;
312 mem = kmap_atomic(page, KM_USER0);
313 if (rw == READ) {
314 copy_from_brd(mem + off, brd, sector, len);
315 flush_dcache_page(page);
316 } else {
317 flush_dcache_page(page);
318 copy_to_brd(brd, mem + off, sector, len);
320 kunmap_atomic(mem, KM_USER0);
322 out:
323 return err;
326 static void brd_make_request(struct request_queue *q, struct bio *bio)
328 struct block_device *bdev = bio->bi_bdev;
329 struct brd_device *brd = bdev->bd_disk->private_data;
330 int rw;
331 struct bio_vec *bvec;
332 sector_t sector;
333 int i;
334 int err = -EIO;
336 sector = bio->bi_sector;
337 if (sector + (bio->bi_size >> SECTOR_SHIFT) >
338 get_capacity(bdev->bd_disk))
339 goto out;
341 if (unlikely(bio->bi_rw & REQ_DISCARD)) {
342 err = 0;
343 discard_from_brd(brd, sector, bio->bi_size);
344 goto out;
347 rw = bio_rw(bio);
348 if (rw == READA)
349 rw = READ;
351 bio_for_each_segment(bvec, bio, i) {
352 unsigned int len = bvec->bv_len;
353 err = brd_do_bvec(brd, bvec->bv_page, len,
354 bvec->bv_offset, rw, sector);
355 if (err)
356 break;
357 sector += len >> SECTOR_SHIFT;
360 out:
361 bio_endio(bio, err);
364 #ifdef CONFIG_BLK_DEV_XIP
365 static int brd_direct_access(struct block_device *bdev, sector_t sector,
366 void **kaddr, unsigned long *pfn)
368 struct brd_device *brd = bdev->bd_disk->private_data;
369 struct page *page;
371 if (!brd)
372 return -ENODEV;
373 if (sector & (PAGE_SECTORS-1))
374 return -EINVAL;
375 if (sector + PAGE_SECTORS > get_capacity(bdev->bd_disk))
376 return -ERANGE;
377 page = brd_insert_page(brd, sector);
378 if (!page)
379 return -ENOMEM;
380 *kaddr = page_address(page);
381 *pfn = page_to_pfn(page);
383 return 0;
385 #endif
387 static int brd_ioctl(struct block_device *bdev, fmode_t mode,
388 unsigned int cmd, unsigned long arg)
390 int error;
391 struct brd_device *brd = bdev->bd_disk->private_data;
393 if (cmd != BLKFLSBUF)
394 return -ENOTTY;
397 * ram device BLKFLSBUF has special semantics, we want to actually
398 * release and destroy the ramdisk data.
400 mutex_lock(&brd_mutex);
401 mutex_lock(&bdev->bd_mutex);
402 error = -EBUSY;
403 if (bdev->bd_openers <= 1) {
405 * Kill the cache first, so it isn't written back to the
406 * device.
408 * Another thread might instantiate more buffercache here,
409 * but there is not much we can do to close that race.
411 kill_bdev(bdev);
412 brd_free_pages(brd);
413 error = 0;
415 mutex_unlock(&bdev->bd_mutex);
416 mutex_unlock(&brd_mutex);
418 return error;
421 static const struct block_device_operations brd_fops = {
422 .owner = THIS_MODULE,
423 .ioctl = brd_ioctl,
424 #ifdef CONFIG_BLK_DEV_XIP
425 .direct_access = brd_direct_access,
426 #endif
430 * And now the modules code and kernel interface.
432 static int rd_nr;
433 int rd_size = CONFIG_BLK_DEV_RAM_SIZE;
434 static int max_part;
435 static int part_shift;
436 module_param(rd_nr, int, S_IRUGO);
437 MODULE_PARM_DESC(rd_nr, "Maximum number of brd devices");
438 module_param(rd_size, int, S_IRUGO);
439 MODULE_PARM_DESC(rd_size, "Size of each RAM disk in kbytes.");
440 module_param(max_part, int, S_IRUGO);
441 MODULE_PARM_DESC(max_part, "Maximum number of partitions per RAM disk");
442 MODULE_LICENSE("GPL");
443 MODULE_ALIAS_BLOCKDEV_MAJOR(RAMDISK_MAJOR);
444 MODULE_ALIAS("rd");
446 #ifndef MODULE
447 /* Legacy boot options - nonmodular */
448 static int __init ramdisk_size(char *str)
450 rd_size = simple_strtol(str, NULL, 0);
451 return 1;
453 __setup("ramdisk_size=", ramdisk_size);
454 #endif
457 * The device scheme is derived from loop.c. Keep them in synch where possible
458 * (should share code eventually).
460 static LIST_HEAD(brd_devices);
461 static DEFINE_MUTEX(brd_devices_mutex);
463 static struct brd_device *brd_alloc(int i)
465 struct brd_device *brd;
466 struct gendisk *disk;
468 brd = kzalloc(sizeof(*brd), GFP_KERNEL);
469 if (!brd)
470 goto out;
471 brd->brd_number = i;
472 spin_lock_init(&brd->brd_lock);
473 INIT_RADIX_TREE(&brd->brd_pages, GFP_ATOMIC);
475 brd->brd_queue = blk_alloc_queue(GFP_KERNEL);
476 if (!brd->brd_queue)
477 goto out_free_dev;
478 blk_queue_make_request(brd->brd_queue, brd_make_request);
479 blk_queue_max_hw_sectors(brd->brd_queue, 1024);
480 blk_queue_bounce_limit(brd->brd_queue, BLK_BOUNCE_ANY);
482 brd->brd_queue->limits.discard_granularity = PAGE_SIZE;
483 brd->brd_queue->limits.max_discard_sectors = UINT_MAX;
484 brd->brd_queue->limits.discard_zeroes_data = 1;
485 queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, brd->brd_queue);
487 disk = brd->brd_disk = alloc_disk(1 << part_shift);
488 if (!disk)
489 goto out_free_queue;
490 disk->major = RAMDISK_MAJOR;
491 disk->first_minor = i << part_shift;
492 disk->fops = &brd_fops;
493 disk->private_data = brd;
494 disk->queue = brd->brd_queue;
495 disk->flags |= GENHD_FL_SUPPRESS_PARTITION_INFO;
496 sprintf(disk->disk_name, "ram%d", i);
497 set_capacity(disk, rd_size * 2);
499 return brd;
501 out_free_queue:
502 blk_cleanup_queue(brd->brd_queue);
503 out_free_dev:
504 kfree(brd);
505 out:
506 return NULL;
509 static void brd_free(struct brd_device *brd)
511 put_disk(brd->brd_disk);
512 blk_cleanup_queue(brd->brd_queue);
513 brd_free_pages(brd);
514 kfree(brd);
517 static struct brd_device *brd_init_one(int i)
519 struct brd_device *brd;
521 list_for_each_entry(brd, &brd_devices, brd_list) {
522 if (brd->brd_number == i)
523 goto out;
526 brd = brd_alloc(i);
527 if (brd) {
528 add_disk(brd->brd_disk);
529 list_add_tail(&brd->brd_list, &brd_devices);
531 out:
532 return brd;
535 static void brd_del_one(struct brd_device *brd)
537 list_del(&brd->brd_list);
538 del_gendisk(brd->brd_disk);
539 brd_free(brd);
542 static struct kobject *brd_probe(dev_t dev, int *part, void *data)
544 struct brd_device *brd;
545 struct kobject *kobj;
547 mutex_lock(&brd_devices_mutex);
548 brd = brd_init_one(MINOR(dev) >> part_shift);
549 kobj = brd ? get_disk(brd->brd_disk) : ERR_PTR(-ENOMEM);
550 mutex_unlock(&brd_devices_mutex);
552 *part = 0;
553 return kobj;
556 static int __init brd_init(void)
558 int i, nr;
559 unsigned long range;
560 struct brd_device *brd, *next;
563 * brd module now has a feature to instantiate underlying device
564 * structure on-demand, provided that there is an access dev node.
565 * However, this will not work well with user space tool that doesn't
566 * know about such "feature". In order to not break any existing
567 * tool, we do the following:
569 * (1) if rd_nr is specified, create that many upfront, and this
570 * also becomes a hard limit.
571 * (2) if rd_nr is not specified, create CONFIG_BLK_DEV_RAM_COUNT
572 * (default 16) rd device on module load, user can further
573 * extend brd device by create dev node themselves and have
574 * kernel automatically instantiate actual device on-demand.
577 part_shift = 0;
578 if (max_part > 0) {
579 part_shift = fls(max_part);
582 * Adjust max_part according to part_shift as it is exported
583 * to user space so that user can decide correct minor number
584 * if [s]he want to create more devices.
586 * Note that -1 is required because partition 0 is reserved
587 * for the whole disk.
589 max_part = (1UL << part_shift) - 1;
592 if ((1UL << part_shift) > DISK_MAX_PARTS)
593 return -EINVAL;
595 if (rd_nr > 1UL << (MINORBITS - part_shift))
596 return -EINVAL;
598 if (rd_nr) {
599 nr = rd_nr;
600 range = rd_nr << part_shift;
601 } else {
602 nr = CONFIG_BLK_DEV_RAM_COUNT;
603 range = 1UL << MINORBITS;
606 if (register_blkdev(RAMDISK_MAJOR, "ramdisk"))
607 return -EIO;
609 for (i = 0; i < nr; i++) {
610 brd = brd_alloc(i);
611 if (!brd)
612 goto out_free;
613 list_add_tail(&brd->brd_list, &brd_devices);
616 /* point of no return */
618 list_for_each_entry(brd, &brd_devices, brd_list)
619 add_disk(brd->brd_disk);
621 blk_register_region(MKDEV(RAMDISK_MAJOR, 0), range,
622 THIS_MODULE, brd_probe, NULL, NULL);
624 printk(KERN_INFO "brd: module loaded\n");
625 return 0;
627 out_free:
628 list_for_each_entry_safe(brd, next, &brd_devices, brd_list) {
629 list_del(&brd->brd_list);
630 brd_free(brd);
632 unregister_blkdev(RAMDISK_MAJOR, "ramdisk");
634 return -ENOMEM;
637 static void __exit brd_exit(void)
639 unsigned long range;
640 struct brd_device *brd, *next;
642 range = rd_nr ? rd_nr << part_shift : 1UL << MINORBITS;
644 list_for_each_entry_safe(brd, next, &brd_devices, brd_list)
645 brd_del_one(brd);
647 blk_unregister_region(MKDEV(RAMDISK_MAJOR, 0), range);
648 unregister_blkdev(RAMDISK_MAJOR, "ramdisk");
651 module_init(brd_init);
652 module_exit(brd_exit);